U.S. Border Patrol agents escort a group of undocumented immigrants into custody with helicopter support from the U.S. Office of Air and Marine on May 20, 2013 near the U.S.-Mexico border in Havana, Texas. (credit: John Moore/Getty Images)

The money is more than $1.1 billion more than President Barack Obama initially asked for in his budget proposal for the Health and Human Services division that cares for and houses immigrant children caught alone at the border. It would effectively come from yet unspecified changes in mandatory programs.

The number of children found trying to cross the Mexican border without parents has skyrocketed in recent years. Between 2008 and 2011, the number of children landing in the custody of HHS’s Refugee Resettlement fluctuated between 6,000 and 7,500 per year. In 2012 border agents apprehended 13,625 unaccompanied children and that number surged even more — to over 24,000 — last year. The total is expected to be as high as 90,000 this year.

Office of Management and Budget Deputy Director Brian Deese wrote to committee chairwoman Sen. Barbara Mikulski, D-Md., to formally ask for more money on May 30.

The HHS budget approved by the committee would also allow the government to move money from other areas if the flow of child immigrants grows beyond the latest estimate of up to 90,000.

The full Senate will have the final say on its version of the HHS budget. And the House has not yet acted on the issue.

Most children caught crossing the border alone are from Honduras, El Salvador and Guatemala and cannot be quickly repatriated.

Under federal law, the children are supposed to be turned over to HHS within 72 hours. Most are then reunited with parents or other relatives already living in the United States.

Because of the massive influx of children this year, the Border Patrol has been forced to house many children in local patrol stations and recently has moved some young immigrants to Nogales, Arizona, where they are being quartered temporarily in a warehouse.

The administration has turned to the Department of Defense to use three military bases in California, Texas and Oklahoma to temporarily house other children once they are transferred to HHS care.